Methods and systems for leaching a metal-bearing ore for the recovery of a metal value

ABSTRACT

A system and method for recovering a metal value from a metal-bearing ore material are provided. A metal-bearing ore can be mixed with certain substances and to form an agglomerated ore. In an intermediate state, between agglomeration and heap formation, bacteria can be added to the metal-bearing ore material to produce an augmented ore. The augmented ore can then be formed into a heap.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalApplication Ser. No. 61/091,691, filed on Aug. 25, 2008, entitled“System and Method for Biostimulated Heap Leaching of Run of Mine Orefor the Recovery of Metal Values,” which is incorporated by referenceherein.

FIELD OF INVENTION

The present invention generally relates to methods and systems forrecovering metal values from metal-bearing ores and, more specifically,to heap leaching methods and systems employing a bio-augmentationprocess.

BACKGROUND

Heap leaching provides a low-cost method of extracting metal values fromrelatively low-grade metal-bearing materials, and has found particularapplication in the processing of metal-bearing ores. Generally, intraditional heap leaching operations, an ore is mined, crushed, and thentransported to a heap location where it is stacked onto an imperviouspad. A suitable acidic solution is dispensed onto the heap, and theresulting leach solution trickles slowly under the force of gravity tothe pad, which typically has a sloped base to allow the solution to flowinto collection drains for further processing, such as, for example, ina conventional, solvent extraction/electrowinning (SX/EW) process or adirect electrowinning (DEW) process.

Bio-stimulation, in general, provides a method to improve the efficiencyof heap leaching operations. That is, the introduction of a suitablebacterial strain or other microorganism into the process, such as,during an agglomeration step or via a raffinate, may result incatalyzation of the oxidation reaction within the heap. Suchbio-oxidation processes typically involve the use of a cultured strainof high-concentration bacteria.

Currently known bio-stimulation heap leaching processes are suboptimalin a number of respects. For example, notwithstanding advances inbio-oxidation and agglomeration techniques, these processes generallyrange from being time consuming to being cost-inefficient.

Accordingly, there is a need for methods and systems for bio-stimulationheap leaching that maintain the traditional cost-efficiency andsimplicity of heap leaching processes while improving efficiency andmetal recovery capabilities.

SUMMARY

In accordance with various embodiments of the present invention, abio-augmentation process is provided. The process can include mixing ametal-bearing material with certain substances to form an agglomeratedore. The agglomerated ore can then be transported to form a heap. Priorto heap formation, a biomass rich solution effluent generally producedfrom a bioreactor or operating heap leach operation is added to theagglomerated ore to produce a biologically augmented ore. The augmentedore is then progressively formed into a heap. Once the heap is formed,raffinate and nutrients may be delivered to the heap. Finally, metal maybe recovered from the leach solution generated by the heap by utilizinga direct electrowinning (DEW) process or a conventional, solventextraction/electrowinning (SX/EW) process.

In accordance with various embodiments of the present invention, aleaching process can include bio-augmentation. In accordance with anexemplary embodiment, the heap leach operation includes providing anore, agglomerating the ore, adding bacteria or other microorganisms tothe agglomerated ore to form an augmented ore, forming a heap with theaugmented ore, and may further include biologically augmenting the heapthrough addition of at least one bacterial strain or othermicroorganisms to produce a metal-bearing solution.

Further areas of applicability will become apparent from the detaileddescription provided herein. It should be understood that thedescription and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present invention is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present invention, however, may bestbe obtained by referring to the detailed description when considered inconnection with the drawing figures, wherein like numerals denote likeelements and wherein:

FIG. 1 is a flow diagram illustrating a leaching process enhancedthrough bio-augmentation in accordance with various embodiments of thepresent invention;

FIG. 2 is a flow diagram illustrating a leaching process enhancedthrough bio-augmentation in accordance with various embodiments of thepresent invention;

FIG. 3 is a flow diagram illustrating a leaching process enhancedthrough bio-augmentation in accordance with various embodiments of thepresent invention;

FIG. 4 is a graph illustrating data of the recovery of copper inaccordance with various embodiments of the present invention; and

FIG. 5 is a flow diagram illustrating a metal recovery process inaccordance with various embodiments of the present invention.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present invention, its applications, or its uses.It should be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.The description of specific examples indicated in various embodiments ofthe present invention are intended for purposes of illustration only andare not intended to limit the scope of the invention disclosed herein.Moreover, recitation of multiple embodiments having stated features isnot intended to exclude other embodiments having additional features orother embodiments incorporating different combinations of the statedfeatures.

Furthermore, the detailed description of various embodiments hereinmakes reference to the accompanying drawing figures, which show variousembodiments by way of illustration and its best mode. While theseexemplary embodiments are described in sufficient detail to enable thoseskilled in the art to practice the invention, it should be understoodthat other embodiments may be realized and that logical and mechanicalchanges may be made without departing from the spirit and scope of theinvention. Thus, the detailed description herein is presented forpurposes of illustration only and not of limitation. For example, stepsor functions recited in descriptions any method, system, or process, maybe executed in any order and are not limited to the order presented.Moreover, any of the step or functions thereof may be outsourced to orperformed by one or more third parties. Furthermore, any reference tosingular includes plural embodiments, and any reference to more than onecomponent may include a singular embodiment

The present invention generally relates to methods and systems forrecovering metal values from metal-bearing ores and, more specifically,to heap leaching methods and systems employing bio-augmentation. Variousembodiments of the present invention provide a process for recoveringmetals value through bacteria bio-augmented heap leaching, conditioning,and electrowinning. These improved methods and systems disclosed hereinachieve an advancement in the art by providing metal value recoverymethods and/or systems that enable significant enhancement in metalvalue yield as compared to conventional metal value recovery methods andsystems.

In accordance with various embodiments of the present invention,bio-augmentation is provided where a metal-bearing material is mixedwith certain substances to form an agglomerated ore. The agglomeratedore is then subjected to bio-augmentation prior to being formed into aheap or transported to an existing heap or leach stockpile system. In anaspect of the present invention, during transportation, betweenagglomeration and heap formation, an effluent solution generated in abioreactor or from a heap leaching process is added to the agglomeratedore to produce a biologically augmented ore. The augmented ore is formedinto a heap or layered upon an existing heap. Once the heap is formed orat the completion of any stage at which metal recovery may commence, aninoculant may be delivered to the heap. The innoculant may comprise araffinate and/or nutrients. Finally, a metal value may be recovered fromthe solution generated by the heap leaching process by utilizing adirect electrowinning (DEW) process or a conventional, solventextraction/electrowinning (SX/EW) process.

Various embodiments of the present invention exhibit significantadvancements over prior art processes, particularly with regard to metalrecovery and process efficiency. In accordance with an exemplaryembodiment of the present invention, a process for recovering a metalvalue from a metal-bearing material includes the steps of: (i)agglomerating a metal-bearing material to form an agglomeratedmetal-bearing material; (ii) bio-augmenting the agglomeratedmetal-bearing material prior to forming a heap; (iii) forming the heapor a portion of the heap; (iv) leaching the heap to yield ametal-containing solution; (v) conditioning the metal-containingsolution without the use of solvent/solution extraction to yield ametal-bearing solution; and (vi) electrowinning the metal-bearingsolution to yield a metal value and a metal-bearing lean electrolytestream. The process can further include treating at least a portion ofthe lean electrolyte stream using a solvent/solution extractiontechnique. In an aspect of this exemplary embodiment, the agglomeratedmetal-bearing material is augmented while being transported to the heap.

In an another exemplary embodiment, a process for recovering a metalvalue from a metal-bearing material includes the steps of: (i)agglomerating a metal-bearing material to form an agglomeratedmetal-bearing material; (ii) bio-augmenting the agglomeratedmetal-bearing material prior to forming a heap; (iii) forming the heapor a portion of the heap; (iv) leaching the heap to yield ametal-bearing solution; (v) treating at least a portion of ametal-bearing solution from the leaching step in a solvent/solutionextraction and electrowinning operation; and (vi) recovering a metalvalue from the metal-bearing solution. In an aspect of this exemplaryembodiment, the agglomerated metal-bearing material is biologicallyaugmented while being transported to the heap.

Examples of metal values include, but are not limited to, copper,nickel, zinc, silver, gold, germanium, lead, arsenic, antimony,chromium, molybdenum, rhenium, tungsten, iron, ruthenium, osmium,cobalt, rhodium, iridium, palladium, platinum, uranium, and/or rareearth metals. More preferably, the metal values can be copper, nickel,and/or zinc. Most preferably, the metal value is copper.

Referring now to FIG. 1, a bio-augmentation leaching process 200 isillustrated according to various embodiments of the present invention.In accordance with various aspects of the embodiments, a metal-bearingmaterial 202 may be provided for processing from which copper and/orother metal values may be recovered. Metal-bearing material 202 may bean ore, a concentrate, a process residue, or any other material fromwhich metal values may be recovered. Metal values, such as thosedescribed herein, may be recovered from metal-bearing material 202. Inan aspect of the present invention, metal-bearing material 202 comprisesa refractory metal sulfide.

In accordance with various embodiments, the metal-bearing material 202can comprise chalcocite, pyrite, chalcopyrite, arsenopyrite, bornite,covellite, digenite, cobaltite, enargite, galena, greenockite,millerite, molybdentite, orpiment, pentlandite, pyrrhotite, sphalerite,stibnite, and/or any other suitable metal-bearing ore material.Preferably, the metal-bearing ore comprises primary or secondarysulfides such as chalcocite, bornite, pyrite, or chalcopyrite, or ablend of such mineral species.

Various aspects and embodiments of the present invention, however, proveespecially advantageous in connection with the recovery of copper fromcopper sulfide ores, such as, for example, chalcopyrite (CuFeS₂),chalcocite (Cu₂S), bornite (Cu₅FeS₄), covellite (CuS), enargite(Cu₃AsS₄), digenite (Cu₉S₅) and mixtures thereof. Thus, metal-bearingmaterial 202 may be a copper ore or concentrate, and preferably, is acopper sulfide ore or concentrate.

Metal-bearing material 202 may comprise ore in a number of states.Before an ore deposit is mined, the ore is said to be in an in-situstate. During mining, metal-bearing material 202 may progress throughmultiple states as it is harvested, collected, transported, andprocessed. For example, metal-bearing material 202 as harvested at themining site is often referred to as run of mine (or “ROM”) ore. ROM oreis produced by, for example, blasting, open pit mining, and othersurface and subterranean ore extraction techniques. As such, ROM oreincludes ore of various sizes from ore as small as powder up to andincluding boulders.

In an aspect of the present invention, all or a portion of metal-bearingmaterial 202 may be further processed via size classification and/orcrushing to achieve a desired particle size distribution, such that,substantially all of the particles are of a size to allow effectiveagglomeration 210 of metal-bearing material 202 during agglomeration 210and allow for optimal economic recovery of the contained metal values.

In accordance with various embodiments of the present invention,metal-bearing material 202 has a particle distribution of anycombination of particle distributions. The particle distribution mayhave a combination of fine and coarse particles. Any particledistribution that maximizes bio-oxidation and metal recovery is useful.A preferred particle distribution allows oxygen and nutrients topermeate through heap 230 for a desirable environment for bacteria 302growth and optimum bio-oxidation activity, while maximizing copperrecovery.

In accordance with various embodiments, metal-bearing material 202 issubjected to agglomeration 210 which serves to combine metal-bearingmaterial 202 with water 204 and acid 206 to form an agglomerated ore208. As will be appreciated by those skilled in the art, water 204 andacid 206 can be mixed into a solution prior to combination withmetal-bearing material 202. In an exemplary embodiment, raffinateprovided from any other metal recovery process (not shown) may be usedto form agglomerated ore 208 and as such, raffinate may comprise bothwater 204 and acid 206. In an aspect of this exemplary embodiment, atleast one of water 204 and acid 206 can be admixed with raffinate andcombined with metal-bearing material 202 to form agglomerated ore 208.In various embodiments, raffinate can be an aqueous product of a solventextraction process, such as, for example, a SX/EW process.

In an aspect of the invention, agglomeration 210 involves metal-bearingmaterial 202 being combined with water 204 and acid 206 in anagglomeration drum. An agglomeration drum may be any suitableagglomeration drum known in the art. In accordance with an exemplaryembodiment, water 204 and acid 206 may be combined with themetal-bearing material 202 within the agglomeration drum. The quantityof the water 204 and the quantity and strength of the acid 206 vary withrespect to the type of metal-bearing material 202 used. In this regard,raffinate may be mixed with at least one of water 204 and acid 206,which may optimize the aqueous solution that is utilized duringagglomeration 210. Metal-bearing material 202 is mixed with the water204 and acid 206 in the agglomeration drum to produce an agglomeratedore 208. Agglomeration 210 may also include the blending of coarseportions and fine portions of metal-bearing material 202, in order tomaximize metal recovery while maintaining heap permeability.

In an aspect of the invention, agglomerated ore 208 can be transportedto heap 230 via a conveyor belt. It should be understood that anysuitable intermediate state would suffice for the transport ofagglomerated ore 208 to heap 230. While agglomerated ore 208 istransported to heap 230, effluent solution 212 may be applied using anysuitable application method including, but not limited to, irrigationlines, streams, sprayers, drip lines, misters, and the like. In anexemplary embodiment, effluent solution 212 may be applied ontoagglomerated ore 208 on the conveyor belt via low pressure spraynozzles. A hood over the spray area may be utilized to contain the sprayof effluent solution 212 under windy conditions. Bio-augmentation 220can also be performed at or near the end of agglomeration 210. In anaspect of the present invention, bio-augmentation 220 occurs at or nearthe end of the time agglomerated ore 208 is in an agglomeration drum oragglomeration apparatus.

Referring again to FIG. 1 after agglomerated ore 208 has been prepared,it may be transported to a heap 230. In accordance with the presentinvention in its various aspects, agglomerated ore 208 is subjected tobio-augmentation 220 prior to being stacked or formed into heap 230.Bio-augmentation 220, as used herein, refers to any process or methodthat provides bacteria or archaea or any other suitable microorganism toagglomerated ore 208. For example, bio-augmentation 220, can be anyprocess or method that inoculates agglomerated ore 208 with at least onestrain of bacteria or archaea. In accordance with exemplary embodiments,bio-augmentation 220 comprises augmenting agglomerated ore 208 witheffluent solution 212 comprising bacteria to form augmented ore 214.

In accordance with various embodiments of the present invention, anyform of microorganism, including but not limited to bacteria or archaea,known or developed hereafter that is useful in leaching a metal may beused to form an effective biological culture to facilitatebio-augmentation 220. The following bacteria and archaea are exemplary:

-   Group A: Acidithiobacillus ferrooxidans; Acidithiobacillus    thiooxidans; Acidithiobacillus organoparus; Acidithiobacillus    acidophilus; Acidithiobacillus caldus; Thiobauillus concretivorus;    Ferrofefunis bagdadii;-   Group B: Leptospirillum ferriphilum, Leptospirillum ferrooxidans,    Leptospirillum sp.-   Group C: Sulfobacillus thermosulfidooxidans; Sulfolobus sp.;-   Group D: Sulfolobus acidicaldarius; Sulfolobus BC; Sulfolobus    solfataricus; and Acidianus brierleyi and the like.

These bacteria and archaea are generally available, for example, fromAmerican Type Culture Collection, or like culture collections, or areknown in the art.

Alternatively, such bacteria and archaea may be obtained from anaturally occurring source and then cultured, or otherwise grown in anyconventional, now known, or hereafter devised method. For example, incertain applications, naturally occurring biological strains may beused. In accordance with various embodiments, mixed bacterial strainsoccurring naturally in raffinate streams may be initially added to anaqueous solution and allowed to undergo a natural selection process.Such selection process may involve, among other things, the reactionenvironment. It has been found that such naturally occurringmicroorganisms may be particularly useful in connection withapplications of the present invention in connection with miningactivities. However, microorganisms such as the above mentionedbacterial and archeal strains may be selected by any technique now knowor developed in the future. In accordance with an exemplary embodimentof the invention, at least one bacterial and/or archeal strain may beselected from the list provided above.

These microorganisms may be classified in terms of their temperaturetolerances and optimized growth and activity ranges as follows:mesophiles, moderate thermophiles, and extreme thermophiles. Mesophilicbacteria generally thrive under moderate operating temperatures, forexample, less about than 40° C.; moderate thermophiles are generallyoptimized for higher temperature conditions, for example, about 37° C.to about 60° C.; and, extreme thermophiles of the archaea class,generally thrive at higher temperatures, for example greater than about55° C. Group A and B bacteria are generally considered mesophilic andare grow under conditions at or below about 40° C.; Group C bacteria arerepresentative of the moderate thermophilic type and are preferablyoperated under conditions at or below about 60° C.; and, Group D archaeaare representative of the extreme thermophile group and grow underconditions from about 60° C. to about 80° C.

Various mixtures of microorganisms from various groups can also beobtained. For example, various mixtures of mesophilic bacteria andmoderately thermophilic bacteria may be mixed together to provide activebacteria variations in temperature of heap 230 during leaching. Forexample, if the temperature of the heap 230 varies between 35° C. and45° C., such a mixture of bacteria would allow for leaching of a metalwithin the range of the temperature variation.

In accordance with an aspect of the present invention, a mixture ofbacteria can be utilized under varying operating conditions of heap 230.For example, mixtures of bacteria in groups A and B may be used. Forexample, if conditions of heap 230 include high ferric-ferrous ironratios, bacteria group B may be better suited for leaching under suchconditions. If ferric-ferrous iron rations are low, bacteria group A maybe more efficient in leaching a metal value from heap 230. Furthermore,if the pH of heap 230 fluctuates, a combination of bacteria in groups Aand B may be effective in leaching. Since sulfide oxidation optimallytakes place at a pH of less than about 2.5 and may be more efficient ina range from about 1.2 to about 2.0, only bacteria that can survive insuch harsh environments may be utilized for leaching metal value fromheap 230. For example, when the pH moves closer to 2, bacteria in groupB may be more efficient, as opposed to when the pH moves closer to 1.2,the bacteria of group A may be more efficient. Those skilled in the artwill appreciate that any combination of bacteria listed herein as wellas any bacteria known in the art or hereafter to follow, may be usedindividually or in combination for the most effective leaching based onstatic or varying conditions of heap 230.

In accordance with an aspect of the present invention, Acidithiobacilluscaldus bacteria can be utilized under operating conditions at or about40° C. For example, a suitable biological environment has been preparedby collecting and culturing mine water containing such bacteria in aconventional manner using methods now known or hereafter developed. Inaccordance with various embodiments of the present invention, a biomassconcentration on the order of from about 1×10⁵ to about 1×10⁹ cells permilliliter of bacteria is preferred but, as will be appreciated by thoseskilled in the art, other biomass concentrations may be utilizeddepending on the individual conditions of a process and/or theconfiguration of a system.

However, any bacteria selection and growth processes now known ordeveloped in the future may be used in accordance with the presentinvention. Moreover, the listings of bacteria and temperature-basedclassifications set forth herein are provided for illustration only, andare not in any way limiting of the bacteria that may be used inaccordance with the present invention. Any biological mediated methodthat utilizes at least one microbial agents, microorganisms, bacteria,archaea, combinations thereof and the like, which are capable of atleast partially oxidizing iron and/or reducing sulfur bearing materials,may be used in accordance with the methods herein described.

As will be discussed in further detail herein, it is desirable toestablish a substantially self-sustaining bacteria population tofacilitate bio-augmentation 220. The sustainability of such a populationmay be promoted by adjusting various parameters of a reactionenvironment in a bioreactor 310, including, for example, controllingtemperature, oxygen availability, agitation, and nutrient addition.

As will be appreciated by those skilled in the art, bioreactors forculturing and/or maintaining a colony or population of active bacteriaare well-known in the art. Any such bioreactor that may be useful togrow and maintain a population of active bacteria that will be useful inheap 230 may be used in accordance with the present invention. As usedherein, a bioreactor is any device or system that supports growth and/ormaintenance of active bacteria. A bioreactor typically includes inletsfor nutrients, oxygen, carbon dioxide, an acid, and/or a base, of whichflow rates can be controlled and, in some cases, monitored. Control ofthe bioreactor for temperature, pH, and dissolved oxygen content may bedesired. In addition, a bioreactor is typically agitated and speeds andcirculation rates will be closely monitored and controlled. Typically,bioreactors used in the industry are vessels which include sensors andcontrol systems, such that the environment in which active bacteria aregrown and/or maintained is tightly controlled for maximum yield ofbacteria and minimal mutation thereof. Further, in various embodiments,a bioreactor may receive a portion of ore, water, or metal-bearingmaterial 202.

As will be appreciated, aeration connected to a bioreactor can provideboth oxygen and circulation to the solution in the bioreactor. Ingeneral, oxygen delivery requirements are a function of, among otherthings, the oxygen requirements for optimized bacterial growth andactivity as well as oxygen requirements for sulfur and/or iron oxidationreaction. The amount of oxygen dissolved in the solution may affect thekinetics of bacterially augmented leaching. For example, in general, theoxidation rate increases as dissolved oxygen increases, up to a valuewhere mass transfer of oxygen is no longer rate determining. The exactvalue of this requirement is dependent upon many factors, includingconcentration of dissolved solids in solution, the bacteria populationand activity, the temperature, agitation, and other such solutionconditions. Elevation, vessel design, and the amount of dissolved oxygenalso affects the active state of bacteria. For example, after reachingthe active bio-oxidation stage of its life cycle, bacteria may lapseinto dormant stage or die if oxygen concentrations fall below a criticalvalue. Once such a dormant stage is reached, bacteria may be slow torecover once higher oxidation concentrations are subsequently restored.

Referring now to FIG. 2, in accordance with various embodiments,effluent solution 212 may be produced in bio-augmentation plant 300.Bio-augmentation plant 300 comprises at least one bioreactor 310 andeffluent holding tank 320. Bioreactor 310 and effluent holding tank 320comprise any suitable bioreactor or effluent holding tank known in theart or hereafter developed. Bioreactor 310 may comprise a source ofbacteria 302, a source of water 304, a source of nutrients 306, and asource of air 308. Bioreactor 310 can further contain an agitator, whichmay be utilized to mix the ingredients within bioreactor 310. Heatexchanger 330 may be coupled with bioreactor 310 to circulate hot liquid312, the purpose of which will be further discussed herein.

Effluent solution 212 may be prepared by adding bacteria 302, water 304,and nutrients 306 into bioreactor 310. Various strains of bacteria 302as discussed herein may be useful depending upon the nature of theMetal-bearing material 202 and the conditions under which bio-oxidationoccurs. Examples of bacteria 302 may include thiobacillus,leptospirillum, and/or sulfobacillus sp. as discussed above. Variousstrains of bacteria or archaea or other appropriate microorganisms 302may be suitable for catalyzing oxidation reactions, including variousmesophiles, thermophiles, and/or the like as discussed above. Ingeneral, the kinetics of biological oxidation may be a function of anyone or more conditions, such as, for example, but not limited to: oremineralogy, solution chemistry temperature, pH, dissolved oxygenconcentration, mass transfer, and/or metal-bearing material 202 particlesize.

Though bio-oxidizing biological materials, including bacteria, archaea,or other suitable microorganisms, derive energy, in part, from theoxidation of sulfur or iron, additional nutrients 306 may aid in cellgrowth and oxidation functions. In various embodiments, nutrients 306may comprise pyrite, elemental sulfur, ferrous iron, ammonium sulfate,potassium sulfate, ammonia, phosphate, potassium, and/or magnesium.Nutrients 306 may be mixed prior to entry into bioreactor 310 or may beadded individually into bioreactor 310. Nutrients 306 may be mixed inany manner known in the art. Nutrients 306 provide material to enablepopulation growth and/or energy generation for bacteria 302.

However, other nutrient constituents and concentrations may be used,depending on the precise requirements and conditions of the desiredsystem. For example, the nutrient constituents of ambient air, such ascarbon dioxide, may also be used to enrich the reaction media. Otherforms of enriched air may also be used in accordance with the presentinvention, including, for example, enriched carbon dioxide and/orenriched oxygen. However, enrichment of the reaction media may proceedby any other suitable method, now known or developed in the future.

Bio-oxidation rates are subject, in part, to the rate limitingconditions described herein, such as, for example, oxygen mass transferand sulfur substrate availability. In addition, induction times forbio-oxidizing activity, growth cycles, biocide activities, bacteriavariability, and the like, as well as economic considerations, allaffect the rates and duration of bio-oxidation in accordance withvarious embodiments of the present invention.

Still referring to FIG. 2, in an exemplary embodiment, bacteria 302,water 304, and nutrients 306 may be mixed within bioreactor 310 by anagitator to form effluent solution 212. Air source 308 providescompressed air to the bioreactor 310 to further agitate effluentsolution 212 and provide bacteria 302 with oxygen to further enable thegrowth of bacteria 302.

In an exemplary embodiment, hot liquid 312 may be introduced into thebioreactor utilizing heat exchanger 330 and a pump. The hot liquid 312may be in any form that provides heat to bioreactor 310. Hot liquid 312is introduced into bioreactor 310 to encourage population growth ofbacteria 302 contained therein.

Effluent solution 212 passes from bioreactor 310 to effluent holdingtank 320. Effluent holding tank 320 may comprise air source 314, tofurther agitate effluent solution 212 and/or provide bacteria 302 ineffluent solution 212 with oxygen. Effluent solution 212 is applied toagglomerated ore 208 to form augmented ore 214. As discussed herein, inan aspect of the present invention, agglomerated ore 208 is transportedto heap 230 via a conveyor belt and effluent solution 212 is applied toagglomerated ore 208 during transportation to form augmented ore 214.Further, effluent solution 212 can be applied to agglomerated ore 208 inan irrigation solution utilizing low pressure spray nozzles to formaugmented ore 214.

In an exemplary embodiment, effluent solution 212 is at least one of aneffluent from a bioreactor and a raffinate. In an aspect of thisexemplary embodment, effluent solution 212 is only a raffinate.

Referring now to FIGS. 1 and 2, in an exemplary embodiment, augmentedore 214 is formed into heap 230. Although any means of heap constructionmay be used, conveyor belt stacking minimizes compaction of augmentedore 214 within heap 230. Minimizing compaction in the stacking of heap230 can allow oxygen and/or nutrients greater access to bacteria 302throughout heap 230, which allows uniform leaching of heap 230 andimproves metal recovery from heap 230. Other means of stacking such asend dumping with a dozer or top dumping can lead to regions of reducedfluid flow within heap 230 due to increased compaction and degradationof augmented ore 214.

In various embodiments, augmented ore 214 may be placed on a lined leachpad or impermeable geologic formation via conveyor stacking, truckdumping, loader-assisted stacking, and/or a combination thereof. Theheight of heap 230 may range from about 5 meters to about 100 meters,depending upon various factors. In an aspect of the present invention,augmented ore 214 can be layered on top of an existing heap, a partiallyformed heap, a depleted heap, portions thereof, or combinations thereof.

In accordance with an exemplary embodiment, heap 230 may be furtheraugmented via stream 216 after formation. In accordance with anexemplary embodiment, nutrients such as pyrite, ammonium sulphate, andpotassium phosphate may optionally be added to heap 230 via stream 216.Further, in accordance with an exemplary embodiment, heap 230 may befurther augmented by applying raffinate to heap 230 via stream 216, aswill be further discussed below. Stream 216 can be raffinate, raffinateand nutrients, raffinate and acid, or raffinate and bacteria orcombinations thereof. Stream 216 can comprise a bacteria concentrationsignificantly below that of effluent solution 212. Accordingly invarious embodiments, heap 230 yields metal-bearing solution 218.

Now with reference to FIG. 3, a bio-augmentation leaching process 200 isillustrated according to various embodiments of the present invention. Aportion of metal-bearing solution 218, indicated as pregnant leachstream (“PLS”) 228, can be directed to bio-augmentation 220. PLS 228contains at least a portion of bacteria 302. PLS 228 can be combinedwith effluent solution 212 or can be applied separately to agglomeratedore 208. Use of PLS 228 in bio-augmentation 220 may be advantageoussince it may contain a distribution of strains of bacteria 302 which areeffective in leaching. Furthermore, PLS 228 can provide a source of atleast one of acid and water. In accordance with one aspect of thepresent invention, depending on the process and/or apparatus used inconditioning 416, it may be advantageous to direct PLS 228 fromconditioning 416 to bio-augmentation 220. For example, overflow from asolid-liquid phase separation unit or similar apparatus employed inconditioning 416 may be directed to bio-augmentation 220 for use infurther inoculating agglomerated ore 208 with bacteria 302.

PLS 228 and effluent solution 212 may be applied to agglomerated ore208, individually or in any combination using any means describedherein, known to those skilled in the art, or hereafter devised. Forexample, the combination of PLS 228 and effluent solution 212 may beapplied to agglomerated ore 208 moving on a conveyor by use ofirrigation employing, for example, sprayer nozzles above the conveyor.In another example, PLS 228 and effluent solution 212 may be applied toagglomerated ore 208 in series. In this regard, PLS 228 may be appliedbefore effluent solution 212 is applied. The application of PLS 228 toagglomerated ore 208 on a first section of a conveyor adds a portion ofbacteria and acid to begin bio-augmentation 220 and may increase theeffectiveness of effluent solution 212 which is applied to agglomeratedore 208 on a second section of the conveyor. However, effluent solution212 maybe applied before PLS 228. The application of effluent solution212 to agglomerated ore 208 on a first section of a conveyor inoculatesagglomerated ore 208 to begin bio-augmentation 220 and PLS 228 can beapplied on a second section of the conveyor to ensure that effluentsolution 212 does not evaporate during transportation to the heap 230.

The Examples set forth herein are illustrative of conventional heapleaching techniques and various aspects of certain preferred embodimentsof the present invention. The process conditions and parametersreflected therein are intended to exemplify various aspects of theinvention, and are not intended to limit the scope of the claimedinvention.

As discussed above, conventional heap leaching techniques areunsatisfactory in a number of ways. The first two examples listed below,Examples 1 and 2, contain test data from conventional heap leachingtechniques. The second two examples listed below, Examples 3 and 4,contain test data from bio-augmentation heap leaching techniques of thepresent invention.

EXAMPLE 1

An example of a heap leaching technique employs the introduction of asuitable bacterial strain into the process, generally via a raffinate,during an agglomeration step. Specifically, a heap leach test wasperformed utilizing a raffinate in the agglomeration step and araffinate in the irrigation solution. The results of such test indicatedby reference numeral 1 in FIG. 4.

EXAMPLE 2

An example of a heap leaching technique employs the introduction of asuitable bacterial strain into the process, generally during anagglomeration step. Specifically, a heap leach test was performedutilizing raffinate at 0.50% bacteria in the agglomeration step and araffinate in the irrigation solution. The results of such test indicatedby reference numeral 2 in FIG. 4.

EXAMPLE 3

An example of a bio-augmentation heap leach employs the introduction ofbacteria in the irrigation solution. Specifically, a heap leach test wasperformed utilizing raffinate in the agglomeration step and a raffinateat 0.01% bacteria in the irrigation solution. The irrigation solution ofExample 3 was continuously applied. The results of such test indicatedby reference numeral 3 in FIG. 4.

EXAMPLE 4

An example of a bio-augmentation heap leach employs the introduction ofbacteria in the irrigation solution. Specifically, a heap leach test wasperformed utilizing raffinate and 5 kg/t acid in the agglomeration stepand a raffinate at 1.00% bacteria in the irrigation solution. Theirrigation solution of Example 4 was applied for 2 days. The results ofsuch test indicated by reference numeral 4 in FIG. 4.

As illustrated in FIG. 4, the copper recovery is greater in Examples 3and 4 employing exemplary embodiments of the present invention than inconventional heap leaching techniques described in Examples 1 and 2.

For ease of discussion, the description of various exemplary embodimentsof the present invention herein generally focuses on the recovery ofdesired metal values from chalcopyrite-containing ore or concentrate;however, any suitable metal bearing material may be utilized. Inaccordance with an exemplary embodiment, metal values from themetal-bearing product stream are removed during an electrowinning step,either with or without a solution conditioning step such as solventextraction or ion exchange, to yield a pure, cathode copper product or acopper powder product.

Referring now to FIG. 5, metal recovery process 400 may be any processfor recovering copper and/or other metal values, and may include anynumber of preparatory or conditioning steps. For example, metal-bearingsolution 218 may be prepared and conditioned for metal recovery throughone or more chemical and/or physical processing steps. Metal-bearingsolution 218 from bio-augmentation heap leaching process 200 may beconditioned to adjust the composition, component concentrations, solidscontent, volume, temperature, pressure, and/or other physical and/orchemical parameters to desired values and thus to form a suitablemetal-bearing solution. Generally, a properly conditioned metal-bearingsolution 218 will contain a relatively high concentration of solublecopper in, for example, an acid sulfate solution, and preferably willcontain few impurities. In accordance with one aspect of an exemplaryembodiment of the invention, however, impurities in the conditionedmetal-bearing solution ultimately may be decreased through the use of aseparate solvent/solution extraction stage, as discussed herein.Moreover, the conditions of metal-bearing solution 218 preferably arekept substantially constant to enhance the quality and uniformity of thecopper product ultimately recovered.

Referring to FIGS. 1-3 and 5, in accordance with various aspects of thepresent invention, a metal-bearing material 202 is provided forprocessing in accordance with metal recovery process 400. Metal-bearingmaterial 202 may be an ore, a concentrate, or any other material fromwhich metal values may be recovered, as discussed herein. Metal valuessuch as, for example but not limited to, copper, gold, silver, platinumgroup metals, nickel, cobalt, molybdenum, rhenium, uranium, rare earthmetals, and the like, may be recovered from metal-bearing material 202in accordance with various embodiments of the present invention. Variousaspects and embodiments of the present invention, however, proveespecially advantageous in connection with the recovery of copper fromcopper sulfide concentrates and/or ores, such as, for example,chalcopyrite (CuFeS₂), chalcocite (Cu₂S), bornite (Cu₅FeS₄), covellite(CuS), enargite (Cu₃AsS₄), digenite (Cu₉S₅), and/or mixtures thereof.Thus, in various embodiments, metal-bearing material 202 is a copper oreor concentrate, and in an exemplary embodiment, metal-bearing material202 is a copper sulfide ore or concentrate.

With reference to FIG. 5, metal recovery process 400 is illustratedaccording to various embodiments of the present invention. Metalrecovery process 400 comprises leach process 200, conditioning 416, andmetal-recovery 418. In various embodiments, leach process 200 can be anymethod, process, or system as presented herein that enables a metalvalue to be leached from a metal-bearing material.

In accordance with various embodiment of the present invention, leachprocess 200 comprises a bio-augmentation heap leaching process. Inaccordance with an exemplary embodiment, the bio-augmentation heapleaching process can comprise providing an metal-bearing material 202 orore, agglomerating the metal-bearing material 202 or ore, addingbacteria to the agglomerated ore 208 to form augmented ore 214, formingheap 230 with augmented ore 214, and may further include augmenting heap230 to produce metal-bearing solution 218, as discussed herein.

In various embodiments, leaching 200 provides metal bearing solution 218for conditioning 416. In various embodiments, conditioning 416 can befor example, but is not limited to, a solid liquid phase separationstep, a pH adjustment step, a dilution step, a concentration step, ametal precipitation step, a filtration step, a settling step, atemperature adjustment step, a solution/solvent extraction step, an ionexchange step, a chemical adjustment step, a purification step, aprecipitation step, and the like, as well as, combinations thereof. Inan exemplary embodiment in which conditioning produces a solid productby, for example, selective precipitation, conditioning 416 can include asolid liquid phase separation step configured to yield metal richsolution 417 and a metal bearing solid. In various embodiments, such as,for example, when a precipitate is formed, the conditioning 416 mayinclude a solid-liquid phase separation. In an exemplary embodiment,conditioning 416 includes a settling/filtration step. In variousembodiments, conditioning 416 produces metal-rich solution 417.

In various embodiments, metal-rich solution 417 may be subjected tometal recovery 418 to yield metal value 440. In exemplary embodiments,metal recovery 418 can comprise electrowinning metal-rich solution 417to yield recovered metal value 440 as a cathode. In one exemplaryembodiment, metal recovery 418 may be configured to employ conventionalelectrowinning processes and include a solvent extraction step, an ionexchange step, an ion selective membrane, a solution recirculation step,and/or a concentration step. In one preferred embodiment, metal recovery418 may be configured to subject metal-rich solution 417 to a solventextraction step to yield a rich electrolyte solution, which may besubject to an electrowinning circuit to recover a desired metal value440. In another exemplary embodiment, metal recovery 418 may beconfigured to employ direct electrowinning processes without the use ofa solvent extraction step, an ion exchange step, an ion selectivemembrane, a solution recirculation step, and/or a concentration step. Inanother preferred embodiment, metal recovery 418 may be configured tofeed metal-rich solution 417 directly into an electrowinning circuit torecover a desired metal value 440. In an especially preferredembodiment, metal value 440 is copper.

With further reference to FIG. 5, metal-rich solution 417 may besuitably treated in metal-recovery 418 to advantageously enable therecovery of a metal value 440, such as, for example, a copper value. Inone exemplary embodiment, metal-recovery 418 comprises directelectrowinning (DEW). In another exemplary embodiment, metal-recovery418 comprises solvent extraction and electrowinning (SX/EW). In anotherexemplary embodiment, metal-recovery 418 is configured to produce acopper powder.

As discussed above, the present invention includes a heap leachingprocess utilizing bio-augmentation to improve the efficiency of metalextraction operations. The present invention has been described withreference to various exemplary embodiments. However, many changes,combinations, and modifications may be made to the exemplary embodimentswithout departing from the scope of the present invention. For example,the various components may be implemented in alternate ways. Thesealternatives can be suitably selected depending upon the particularapplication or in consideration of any number of factors associated withthe operation of the system. In addition, the techniques describedherein may be extended or modified for use with other metal extractionprocesses. These and other changes or modifications are intended to beincluded within the scope of the present claims.

The present invention has been described above with reference to anumber of exemplary embodiments. It should be appreciated that theparticular embodiments shown and described herein are illustrative ofthe invention and its best mode and are not intended to limit in any waythe scope of the invention as set forth in the claims. Those skilled inthe art having read this disclosure will recognize that changes andmodifications may be made to the exemplary embodiments without departingfrom the scope of the present invention. For example, various aspectsand embodiments of this invention may be applied to recovery of metalsother than copper, such as nickel, zinc, cobalt, and others. Althoughcertain preferred aspects of the invention are described herein in termsof exemplary embodiments, such aspects of the invention may be achievedthrough any number of suitable means now known or hereafter devised.Accordingly, these and other changes or modifications are intended to beincluded within the scope of the present invention.

It is believed that the disclosure set forth above encompasses at leastone distinct invention with independent utility. While the invention hasbeen disclosed in the exemplary forms, the specific embodiments thereofas disclosed and illustrated herein are not to be considered in alimiting sense as numerous variations are possible. Equivalent changes,modifications and variations of various embodiments, materials,compositions and methods may be made within the scope of the presentinvention, with substantially similar results. The subject matter of theinventions includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/orproperties disclosed herein.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any element orcombination of elements that may cause any benefit, advantage, orsolution to occur or become more pronounced are not to be construed ascritical, required, or essential features or elements of any or all theclaims or the invention. Many changes and modifications within the scopeof the instant invention may be made without departing from the spiritthereof, and the invention includes all such modifications.Corresponding structures, materials, acts, and equivalents of allelements in the claims below are intended to include any structure,material, or acts for performing the functions in combination with otherclaim elements as specifically claimed. The scope of the inventionshould be determined by the appended claims and their legal equivalents,rather than by the examples given above.

What is claimed is:
 1. A method for recovering a metal value from ametal-bearing material, the method comprising: agglomerating ametal-bearing material to form an agglomerated ore; inoculating saidagglomerated ore with bacteria to form an augmented ore; forming atleast a portion of a heap with said augmented ore; leaching said heap toyield a metal-bearing solution, wherein said metal-bearing solutioncomprises a pregnant leach stream; and directing at least a portion ofsaid pregnant leach stream to said agglomerated ore before said step offorming at least a portion of said heap and then repeating said formingand leaching steps.
 2. The method according to claim 1, wherein saidbacteria is provided from at least one of an effluent solution and apregnant leach stream, wherein said effluent solution is from at leastone of a bioreactor, a heap leach, and a raffinate.
 3. The methodaccording to claim 2, wherein said step of inoculating said agglomeratedore with bacteria to form an augmented ore comprises adding at least oneof said effluent solution and said pregnant leach stream to saidagglomerated ore with bacteria to form an augmented ore before said stepof forming at least a portion of a heap.
 4. The method according toclaim 1, further comprising transporting said agglomerated ore duringsaid step of inoculating said agglomerated ore with bacteria to form anaugmented ore.
 5. The method according to claim 4, wherein saidtransporting said agglomerated ore comprises transporting said ore on atleast one conveyor.
 6. The method according to claim 1, furthercomprising adding at least one of a raffinate and a nutrient to saidbacteria in said heap.
 7. The method according to claim 6, wherein saidnutrient comprises at least one of pyrite, ammonium sulfate, andpotassium phosphate.
 8. A method for recovering a metal value from ametal-bearing material, comprising the steps of: agglomerating ametal-bearing material to form an agglomerated ore; adding bacteria tosaid agglomerated ore to form an augmented ore; forming at least aportion of a heap with said augmented ore; leaching said heap to yield ametal-bearing solution, wherein said metal-bearing solution comprises apregnant leach stream; directing at least portion of said pregnant leachstream to said agglomerated ore; conditioning at least a portion of saidpregnant leach stream to yield a conditioned pregnant leach stream; anddirecting at least a portion of said conditioned pregnant leach streamto said agglomerated ore before said step of forming at least a portionof said heap and then repeating said forming and leaching steps.
 9. Themethod according to claim 8, further comprising: conditioning at least aportion of said metal-bearing solution to yield an electrolyte solutionsuitable for electrowinning; and electrowinning said electrolytesolution to yield copper.
 10. The method according to claim 8, whereinsaid conditioning comprises at least one of a solid liquid phaseseparation step, a pH adjustment step, a dilution step, a concentrationstep, a metal precipitation step, a filtration step, a settling step, atemperature adjustment step, a solution/solvent extraction step, an ionexchange step, a chemical adjustment step, a purification step, and aprecipitation step.
 11. A method for preparing a metal-bearing materialfor metal recovery, the method comprising: reducing a coarseness of ametal-bearing material to form a processed metal-bearing material;agglomerating said processed metal-bearing material with at least waterand an acid to form an agglomerated metal-bearing material; andinoculating said agglomerated metal-bearing material with an effluentstream and a pregnant leach stream before forming at least a portion ofa heap to form an augmented metal-bearing material, wherein at least oneof said effluent stream and pregnant leach stream comprises an activebacteria strain operable to bio-leach a metal value from saidmetal-bearing material.
 12. The method according to claim 11, furthercomprising stacking said augmented metal-bearing material to form atleast a portion of said heap.
 13. The method according to claim 12,further comprising optimizing conditions of said active bacteria in saidheap.
 14. The method according to claim 13, wherein the step ofoptimizing conditions of said active bacteria in said heap furthercomprises adding to said heap at least one of a raffinate stream, anutrient stream, an oxygen stream, and combinations thereof.
 15. Themethod according to claim 12, further comprising leaching a metal valuefrom said heap.
 16. The method according to claim 11, further comprisingrecovering at least one metal value.